Semiconductor wafer processing system

ABSTRACT

The embodiments herein relate to methods for processing a wafer through a semiconductor wafer processing system and an apparatus. According to an aspect of the present disclosure, a system for processing a semiconductor wafer is provided. The system includes a heating system, a pressure control system, and a gas flow system. The heating system is configured for heating a chuck. The pressure control system is configured for setting an internal chamber pressure. The gas flow system is configured for inflowing a gas in the process chamber to increase the internal chamber pressure to at least a base pressure. The heating system heats the chuck after the internal chamber pressure reaches the base pressure set by the pressure control system

FIELD OF INVENTION

The present disclosed subject matter relates to a semiconductor waferprocessing system and methods for processing a wafer through such asystem.

BACKGROUND

In semiconductor product manufacturing, semiconductor wafers areprocessed to form integrated circuits thereon. Wafers having asubstantially flat wafer surface topography are generally desired assemiconductor processing tools are designed to process the wafers assuch. For example, photolithography tools and processes are designed toimage on wafers having a substantially flat wafer surface topography inorder to focus on the wafer surfaces. When the warping or the degree ofnon-flatness of the wafer surface exceeds the range of the depth offocus (DOF) of the photolithography system, a mask pattern imaged willbe out of focus in at least some regions on the wafer. This can resultin defects in the subsequent processing and lead to the fabrication ofdefective semiconductor devices.

While unprocessed semiconductor wafers may be initially unstrained,subsequent wafer processing may undesirably warp the wafers. Waferwarpage may occur due to the different thermal responses of materialsthat are formed on the wafer. The different materials having differentcoefficients of thermal expansion will expand/contract at differentrates when heated. When the warpage of the wafer exceeds an acceptabledegree, the wafer may be non-uniformly heated, thereby adverselyimpacting the reliability of the semiconductor devices.

Therefore, it is desirable to provide methods for processing a waferthrough a processing system and an apparatus to overcome, or at leastameliorate, the disadvantage described above. Furthermore, otherdesirable features and characteristics will become apparent from thesubsequent detailed description and the appended claims, taken inconjunction with the accompanying drawings and this background of thedisclosure.

SUMMARY

To achieve the foregoing and other aspects of the present disclosure,methods for processing a wafer through a semiconductor wafer processingsystem and an apparatus are presented.

According to an aspect of the present disclosure, a system forprocessing a semiconductor wafer is provided. The system includes aheating system, a pressure control system, and a gas flow system. Theheating system is configured for heating a chuck. The pressure controlsystem is configured for setting an internal chamber pressure. The gasflow system is configured for inflowing a gas in the process chamber toincrease the internal chamber pressure to at least a base pressure. Theheating system heats the chuck after the internal chamber pressurereaches the base pressure set by the pressure control system.

According to another aspect of the present disclosure, a method forprocessing a semiconductor wafer is provided. The method includesproviding a process chamber having a chuck therein. An internal chamberpressure of the process chamber is set to at least a base pressure. Thechuck is heated after the process chamber reaches the base pressure.

According to yet aspect of the present disclosure, a semiconductorprocessing tool is provided. The tool includes a process chamber and achuck in the process chamber. The process chamber is configured for ahigh-pressure wafer processing operation, wherein an internal chamberpressure can be set to at least a base pressure higher than an ambientpressure. The chuck has grooves in the chuck surface that terminate inthe chuck. The grooves form air pockets when a wafer is placed on thechuck and the air pockets have an air pressure lower than the basepressure.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of the present disclosure will be better understood froma reading of the following detailed description, taken in conjunctionwith the accompanying drawings:

FIG. 1 is a flow chart illustrating a method for processing a waferthrough a processing system, according to an embodiment of thedisclosure.

FIG. 2 is a cross-sectional view of a process chamber having a waferchuck therein, according to an embodiment of the disclosure.

FIG. 3 is a cross-sectional view of a process chamber having a waferchuck therein, according to another embodiment of the disclosure.

FIG. 4 is a graph illustrating a temperature difference between a waferand a reference when subjected to a thermal operation on a wafer chuck,according to an embodiment of the disclosure.

For simplicity and clarity of illustration, the drawings illustrate thegeneral manner of construction, and certain descriptions and details ofwell-known features and techniques may be omitted to avoid unnecessarilyobscuring the discussion of the described embodiments of the device.

Additionally, elements in the drawings are not necessarily drawn toscale. For example, the dimensions of some of the elements in thedrawings may be exaggerated relative to other elements to help improveunderstanding of embodiments of the device. The same reference numeralsin different drawings denote the same elements, while similar referencenumerals may, but do not necessarily, denote similar elements.

DETAILED DESCRIPTION

Various embodiments of the present disclosure are now described indetail with accompanying drawings. It is noted that like andcorresponding elements are referred to by the use of the same referencenumerals. The embodiments disclosed herein are exemplary, and notintended to be exhaustive or limiting to the disclosure. Certainstructures may be conventionally fabricated, for example, using knownprocesses and techniques, and specifically disclosed processes andmethods may be used to achieve individual aspects of the presentdisclosure.

The disclosure relates to a semiconductor processing system and methodsfor processing a wafer through such a system and an apparatus. A wafermay include a plurality of semiconductor devices fabricated thereupon.

The plurality of semiconductor devices may be partially processed. Thoseskilled in the art should readily appreciate that the term“partially-processed wafer” refers to semiconductor devices on asemiconductor wafer during any of the various stages of semiconductorproduct manufacturing to form a variety of different semiconductordevices, including, but not limited to, logic devices, memory devices,etc., and the devices may be either NFET or PFET devices.

The wafer may include a variety of configurations, such as a bulksilicon configuration or a semiconductor-on-insulator (SOI)configuration. The wafer may include any appropriate semiconductormaterial, such as silicon, silicon germanium, silicon carbon, otherII-VI or III-V semiconductor compounds, and the like. Thus, the terms“semiconductor wafer”, “wafer”, “semiconductor substrate”, and“substrate” should be understood to cover all forms of such materials.The wafer may include semiconductor substrates having diameters of 200,300, and 450 mm. However, the present disclosure is not limited to thisand the wafers can have various shapes, sizes, and materials.

FIG. 1 is a flow chart 100 illustrating a method for processing a waferthrough a semiconductor wafer processing system, according to anembodiment of the disclosure. The processing system may include, amongother things, a processing tool with a process chamber, a wafer handlingsystem, a wafer chuck, a wafer heating system, a pressure controlsystem, and a gas flow system. The processing tool may be used as onepart of an elaborate fabrication process to manufacture semiconductorwafers into functional semiconductor devices and various integratedcircuit products.

The wafer may be processed in the process chamber and may have aplurality of partially processed semiconductor devices formed thereupon.The wafer processing operation may include a high-pressure processoperation such as, but not limited to, a diffusion process or anannealing process. As used herein, the term “high-pressure processoperation” refers to a process operation that employs a pressure levelgreater than an ambient pressure of the surroundings in which theprocessing tool is located.

The wafer to be processed may be loaded in the process chamber; theprocess is illustrated as operation 102 in the flow chart 100 shown inFIG. 1. The wafer may be placed on the wafer chuck that is enclosedwithin the process chamber using the wafer handling system. The internalchamber pressure of the process chamber may be substantially equivalentto the ambient pressure. In an embodiment of the disclosure, the ambientpressure may be substantially equivalent to the atmospheric pressure ofthe surroundings.

The process chamber may be pressurized by introducing a pressurizing gasinto the process chamber through the gas flow system after the wafer hasbeen placed on the wafer chuck; the process is illustrated as operations104A and 104B in the flow chart 100 shown in FIG. 1. The gas flow systemmay be controlled by the pressure control system. The pressure controlsystem is capable of setting the internal chamber pressure to apredetermined pressure level and controls the amount of pressurizing gasinflowing to the process chamber. The pressure control system sets theprocess chamber to an internal chamber pressure greater than the ambientpressure. As the pressurizing gas fills the process chamber, theconfined pressurizing gas exerts a force against the inner surfaces ofthe process chamber, including against the wafer that is placed on thewafer chuck. This force advantageously holds the wafer in place as longas the pressurizing gas is not exhausted. In an embodiment of thedisclosure, the process chamber 202 may further include a venting meansto operatively cooperate with the pressure control system to control theinternal chamber pressure.

The pressurizing gas may include a process gas that may be used in thewafer processing operation or an inert gas if no process gas is requiredfor the wafer processing operation. In an embodiment of the disclosure,the pressurizing gas may include hydrogen, deuterium, argon, or gasescontaining fluorine, chlorine, or nitrogen.

In an embodiment of the disclosure, the internal chamber pressure may beset to a process pressure that is required for the wafer processingoperation; the process is illustrated as operation 104A in the flowchart 100 shown in FIG. 1. In an embodiment of the disclosure, theinternal chamber pressure in the process chamber may be set to a basepressure that is lower than the process pressure but higher than theambient pressure; the process is illustrated as operation 104B in theflow chart 100 shown in FIG. 1. The base pressure may be a predeterminedpressure level that is sufficient to hold the wafer stationary on thewafer chuck. For example, the base pressure may be 0.2 MPa.

A thermal operation may be performed on the wafer using the waferheating system; the process is illustrated as operation 106 in the flowchart 100 shown in FIG. 1. The wafer heating system may include aheating element in the wafer chuck. The wafer may be heated to a processtemperature that is required for the wafer processing operation afterthe process chamber reaches the predetermined pressure level set by thepressure control system. The wafer heating system activates the heatingelement in the wafer chuck which in turn heats the wafer that is placedthereupon. The increased internal chamber pressure, besides fixating thewafer on the wafer chuck for the wafer processing operation,advantageously provides a uniform downward force on the upper wafersurface that impedes the warpage of the wafer during the thermaloperation, thereby enabling uniform heating of the wafer by the waferchuck.

The wafer may undergo a wafer processing operation; the process isillustrated as operation 108 in the flow chart 100 shown in FIG. 1. Thewafer processing operation may include a high-pressure process operationsuch as, but not limited to, a diffusion process or an annealingprocess. It is understood that the internal chamber pressure may be setto the required process pressure for the wafer processing operation, asprovided by operation 104C, in the event where the internal chamberpressure was initially increased to the base pressure at operation 104Binstead of to the process pressure at operation 104A.

The process chamber may be cooled and the increased internal chamberpressure may be released after completion of the wafer processingoperation; the process is illustrated as operation 110 in the flow chart100 shown in FIG. 1. The process chamber may be cooled to an idlingtemperature by deactivating the wafer heating system and the increasedinternal chamber pressure may be released by exhausting the pressurizinggas through the gas flow system. The internal chamber pressure isreverted to a pressure level that is substantially equivalent to theambient pressure such that the wafer can be unloaded from the waferchuck at operation 120 using the wafer handling system and proceed tothe next wafer processing operation.

The order in which any operations described in the flow chart 100 ofFIG. 1 is not intended to be construed as a limitation, and any numberof the described operations can be combined in any order to implementthe method. For example, operations 106 and 108 may be performedconcurrently and in parallel. Additionally, individual operations may beremoved from the process without departing from the spirit and scope ofthe subject matter described herein. Furthermore, the method may beimplemented in any suitable hardware, software, firmware, or acombination thereof, without departing from the scope of the invention.

FIG. 2 illustrates a cross-sectional view of a process chamber 202enclosing a wafer chuck 204 therein, according to an embodiment of thedisclosure. The wafer chuck 204 may be configured for the placement of awafer 206 for processing in the process chamber 202. The wafer chuck 204may operatively cooperate with a wafer heating system, such as a heatingelement 208 in the wafer chuck 204, to heat the wafer chuck 204, whichin turn heats the wafer 206, as similarly described in operation 106 ofFIG. 1. The wafer chuck 204 may be annular in shape that conforms to thegenerally annular shape of wafers. However, the disclosure is notlimited to an annular-shaped wafer chuck and the wafer chuck may take onother configurations without departing from the spirit and scope of thepresent disclosure.

The wafer chuck 204 may be enclosed within the process chamber 202 thatis part of a semiconductor processing tool. The process chamber 202 mayinclude a door 210 to transfer the wafer 206 into the process chamber202 for processing and out of the process chamber 202 upon completion ofa wafer processing operation. In an embodiment of the disclosure, theprocess chamber 202 may include a process chamber configured forhigh-pressure wafer processing operations.

The wafer 206 may be loaded into the process chamber 202 through thedoor 210 using a wafer handling system and be placed on an upper surfaceof the wafer chuck 204U, as similarly described in operation 102 ofFIG. 1. During the loading of the wafer 206 into the process chamber202, the internal chamber pressure of the process chamber 202 may besubstantially equivalent to the ambient pressure.

The wafer chuck 204 may have an uneven upper wafer chuck surface 204U,as illustrated in FIG. 2. When the wafer 206 is placed on the waferchuck 204, air gaps 212 may be formed between the upper wafer chucksurface 204U and the lower wafer surface 206L. Although referred to as“air” gaps in this disclosure, the elemental composition of the air caninclude different gases and should not be construed as having anyparticular elemental composition. In accordance with the presentdisclosure, the air gaps are voids where no solid material is present.Any number and type of gases may be present in the air gaps.

The air gaps 212 may have an air pressure that is substantiallyequivalent to the ambient pressure. Since the internal chamber pressuremay be substantially equivalent to the ambient pressure, the force F_(U)exerted on the upper wafer surface 206U by the internal chamber pressuremay be expected to be substantially equivalent to the force F_(L)exerted on the lower wafer surface 206L by the air pressure of the airgaps 212, i.e., F_(U) F_(L). Therefore, the wafer 206 may be easilydisplaced and not fixated on the wafer chuck.

The process chamber 202 may include a gas flow system having an inlet214 to receive a pressurizing gas and an outlet 216 to exhaust thepressurizing gas. The gas flow system may be controlled by the pressurecontrol system. The pressure control system is capable of setting theinternal chamber pressure to a predetermined pressure level and controlsthe amount of pressurizing gas inflowing to the process chamber. Thepressurizing gas may flow into the process chamber 202 through the inlet214 to increase the internal chamber pressure to a pressure levelpredetermined by the pressure control system. The predetermined pressurelevel may be greater than the ambient pressure, as similarly describedin operations 104A, 104B, and 104C of FIG. 1. In an embodiment of thedisclosure, the process chamber 202 may further include a venting meansto operatively cooperate with the pressure control system to control theinternal chamber pressure.

When the pressurizing gas increases the internal chamber pressure, theforce F_(U) exerted on the inner surfaces of the process chamber 202,including against the upper wafer surface 206U increases with theincreasing internal chamber pressure. The force F_(U) is greater thanthe force F_(L) exerted on the lower wafer surface 206L by the airpressure of the air gaps 212, i.e., F_(U)>F_(L). As the wafer 206 issubjected to a greater force F_(U) from the increased internal chamberpressure, the air gaps 212 operatively cooperate with the increasedinternal chamber pressure to securely fixate the wafer 206 on the waferchuck 204.

Upon completion of the wafer processing operation, the pressurizing gasmay be exhausted through the outlet 216 and the internal chamberpressure reverts to a pressure level that is substantially equivalent tothe ambient pressure. The wafer 206 may be unloaded from the wafer chuck204 and proceed to the next wafer processing operation.

FIG. 3 illustrates a cross-sectional view of a process chamber 202enclosing a wafer chuck 304 therein, according to another embodiment ofthe disclosure. Similar to the wafer chuck 204 in FIG. 2, the waferchuck 304 may be configured for placement of a wafer 206 for processing.The wafer chuck 304 may also include a heating element 208 to heat thewafer chuck 304 and the wafer 206, as similarly described in operation106 of FIG. 1.

The difference between the wafer chuck 204 in FIG. 2 and the wafer chuck304 in FIG. 3 lies in that the wafer chuck 304 has grooves 318 formedtherein. The grooves 318 may have a bigger volume than the air gaps 212and may extend from the upper wafer chuck surface 304U and terminatewithin the wafer chuck 304 such that the grooves 318 do not extendthrough the wafer chuck 304. Even though four grooves are beingillustrated in FIG. 3, it is understood that any number of grooves maybe formed in the wafer chuck.

When the wafer 206 is placed on the wafer chuck 304, air pockets areformed in the grooves 318. Similar to the air gaps 212, the air pocketsmay have an air pressure that is substantially equivalent to the ambientpressure. When the internal chamber pressure increases due to the inflowof the pressurizing gas, the air pressure of the air pockets being lowerthan the internal chamber pressure, the force F_(U) exerted on the upperwafer surface 206U is, therefore, greater than the force F_(L) exertedby the air pockets (and the air gaps 212), i.e., F_(U)>F_(L). The airpockets (and the air gaps 212) operatively cooperate with the increasedinternal chamber pressure to securely fixate the wafer 206 on the waferchuck 304. The grooves 318 may be expected to further impede anypotential displacement of the wafer 206 from the wafer chuck 304.

FIG. 4 is a graph 400 illustrating a temperature difference between awafer and a reference when subjected to a thermal operation on a waferchuck in a process chamber, according to an embodiment of thedisclosure. The wafer is loaded on the wafer chuck and the reference, ina form of an unprocessed wafer chip, is placed on the wafer chuck inclose proximity to the wafer. The wafer and the reference are heatedfrom an ambient temperature to a reference temperature of about 420° C.and the temperatures at the wafer edge and the reference are beingmeasured throughout the thermal operation.

The amount of wafer warpage may be indirectly visible from thetemperature difference recorded between the wafer and the referencethroughout the thermal operation. For example, wafer warpage occurs whenthe wafer is non-uniformly heated, thereby resulting in a greatertemperature difference between the wafer and the reference.

Group 402 illustrates the temperature difference between the wafer andthe reference across the range of reference temperature when the waferwas loaded into the process chamber and heated using the methoddisclosed in the present disclosure. The process chamber was pressurizedto at least a base pressure after loading the wafer on the wafer chuckand before heating the wafer. As illustrated, the temperature differencerecorded in Group 402 is relatively narrow. This indicates that thewafer was uniformly heated by the wafer chuck, and minimal wafer warpagewas induced during the thermal operation.

Group 404 illustrates the temperature difference between another waferand the reference across the range of reference temperature when thewafer was loaded into the process chamber and heated withoutpressurizing the process chamber to at least a base pressure beforeheating the wafer. The temperature difference recorded in Group 404, onthe other hand, is substantially wider than the temperature differencerecorded in Group 402. This indicates the wafer was non-uniformly heatedby the wafer chuck, and there was substantial wafer warpage induced dueto the non-uniform heating. It is further noted that there is anincreasing temperature difference recorded with increasing referencetemperature and the greatest temperature difference is recorded at thepeak of about 420° C., which is a typical process temperature of ahigh-pressure wafer processing operation. This further indicates thatthe wafer is substantially warped when heated to that temperature.

Therefore, the embodiments as described above result in advantages, suchas but not limited to, minimized inducement of wafer warpage and uniformheating of the wafer during a wafer processing operation.

As presented in the above disclosure, methods for processing a waferthrough a processing system and an apparatus are presented. Theprocessing system may include a processing tool with a process chamber,a wafer handling system, a wafer chuck, a wafer heating system, apressure control system, and a gas flow system. The processing systemmay be configured for a high-pressure wafer processing operation. Thehigh-pressure wafer processing operations may include but are notlimited to, a diffusion process or an annealing process.

The methods include loading the wafer on the wafer chuck enclosed withinthe process chamber and pressurizing the process chamber by inflowing apressurizing gas to at least a pressure level that is greater than theambient pressure using the gas flow system. The gas flow system may becontrolled by a pressure control system that controls the amount ofpressurizing gas inflowing to the process chamber. The increasedinternal chamber pressure securely fixates the wafer on the wafer chuckas long as the pressurizing gas is not exhausted, without the need foradditional means for fixating the wafer for the wafer processingoperation. The wafer is subsequently heated up to a required processtemperature for the wafer processing operation by the wafer heatingsystem.

The methods of pressurizing the process chamber before heating the waferas disclosed in the present disclosure advantageously minimize waferwarpage, thereby allowing the wafer to be evenly heated for the waferprocessing operation and achieving improved product reliability.

The terms “top”, “bottom”, “over”, “under”, and the like in thedescription and the claims, if any, are used for descriptive purposesand not necessarily for describing permanent relative positions. It isto be understood that the terms so used are interchangeable underappropriate circumstances such that the embodiments of the devicesdescribed herein are, for example, capable of operation in otherorientations than those illustrated or otherwise described herein.

Additionally, the formation of a first feature over or on a secondfeature in the description that follows may include embodiments in whichthe first and second features are formed in direct contact, and may alsoinclude embodiments in which additional features may be formedinterposing the first and second features, such that the first andsecond features may not be in direct contact.

Similarly, if a method is described herein as involving a series ofsteps, the order of such steps as presented herein is not necessarilythe only order in which such steps may be performed, and certain of thestated steps may possibly be omitted and/or certain other steps notdescribed herein may possibly be added to the method. Furthermore, theterms “comprise”, “include”, “have”, and any variations thereof, areintended to cover a non-exclusive inclusion, such that a process,method, article, or device that comprises a list of elements is notnecessarily limited to those elements, but may include other elementsnot expressly listed or inherent to such process, method, article, ordevice. Occurrences of the phrase “in an embodiment” herein do notnecessarily all refer to the same embodiment.

In addition, unless otherwise indicated, all numbers expressingquantities, ratios, and numerical properties of materials, reactionconditions, and so forth used in the specification and claims are to beunderstood as being modified in all instances by language ofapproximation, such as “about”, “approximately”, and “substantially”,and are not to be limited to the precise value specified. The languageof approximation may correspond to the precision of an instrument usedto measure the value and, unless otherwise dependent on the precision ofthe instrument, may indicate +/−10% of the stated value(s).

While several exemplary embodiments have been presented in the abovedetailed description of the device, it should be appreciated that anumber of variations exist. It should further be appreciated that theembodiments are only examples, and are not intended to limit the scope,applicability, dimensions, or configuration of the device in any way.Rather, the above detailed description will provide those skilled in theart with a convenient road map for implementing an exemplary embodimentof the device, it being understood that various changes may be made inthe function and arrangement of elements and method of fabricationdescribed in an exemplary embodiment without departing from the scope ofthis disclosure as set forth in the appended claims.

What is claimed is:
 1. A system for processing a semiconductor wafer,the system comprising: a heating system for heating a chuck; a pressurecontrol system for setting an internal chamber pressure; and a gas flowsystem for inflowing a gas in the process chamber to increase theinternal chamber pressure, wherein the heating system heats the chuckafter the internal chamber pressure reaches at least a base pressure setby the pressure control system.
 2. The system of claim 1, wherein thepressure control system controls the amount of gas inflowing to theprocess chamber from the gas flow system.
 3. The system of claim 1,wherein the internal chamber pressure is set to a pressure level higherthan an ambient pressure.
 4. The system of claim 1, wherein the internalchamber pressure is set to a pressure level lower than a processpressure of a wafer processing operation.
 5. The system of claim 1,wherein the internal chamber pressure is set to a process pressure of awafer processing operation.
 6. The system of claim 1, wherein theheating system comprises a heating element in the chuck.
 7. The systemof claim 1, wherein the gas comprises a process gas for a waferprocessing operation.
 8. The system of claim 1, wherein the gascomprises an inert gas.
 9. The system of claim 1, wherein the gascomprises deuterium.
 10. A method for processing a semiconductor wafer,the method comprising: providing a process chamber having a chucktherein; setting an internal chamber pressure to at least a basepressure; and heating the chuck after the process chamber reaches thebase pressure.
 11. The method of claim 10, wherein setting the internalchamber pressure comprises inflowing a gas into the process chamber. 12.The method of claim 10, wherein the internal chamber pressure is set toa pressure level higher than an ambient pressure.
 13. The method ofclaim 12, wherein internal chamber pressure is set to a pressure levellower than a process pressure for a wafer processing operation.
 14. Themethod of claim 10, wherein the internal chamber pressure is set to aprocess pressure of a wafer processing operation.
 15. The method ofclaim 10, wherein heating the chuck comprises activating a heatingelement in the chuck.
 16. The method of claim 10, further comprisingperforming a high-pressure wafer processing operation on the wafer. 17.A semiconductor processing tool, the tool comprising: a process chamberfor a high-pressure wafer processing operation, wherein an internalchamber pressure can be set to at least a base pressure higher than anambient pressure; and a chuck in the process chamber, the chuck havinggrooves in the chuck surface that terminate in the chuck, wherein when awafer is placed on the chuck, air pockets are formed in the grooveshaving an air pressure lower than the base pressure.
 18. The tool ofclaim 17, wherein the chuck further comprises a heating element, theheating element is activated after the internal chamber pressure reachesthe base pressure.
 19. The tool of claim 17, wherein the high-pressurewafer processing operation comprises a diffusion process.
 20. The toolof claim 17, wherein the high-pressure wafer processing operationcomprises an annealing process.